Dark Matter-Motivated Searches for Exotic 4th Generation Quarks in Tevatron and Early LHC Data

We determine the prospects for finding dark matter at the Tevatron and LHC through the production of exotic 4th generation quarks T' that decay through T' \to t X, where X is dark matter. The resulting signal of t \bar{t} + \met has not previously been considered in searches for 4th generation quarks, but there are both general and specific dark matter motivations for this signal, and with slight modifications, this analysis applies to any scenario where invisible particles are produced in association with top quarks. Current direct and indirect bounds on such exotic quarks restrict their masses to be between 300 and 600 GeV, and the dark matter's mass may be anywhere below m_T'. We simulate the signal and main backgrounds with MadGraph/MadEvent-Pythia-PGS4. For the Tevatron, we find that an integrated luminosity of 20 fb^-1 will allow 3\sigma discovery up to m_T' = 400 GeV and 95% exclusion up to m_T' = 455 GeV. For the 10 TeV LHC with 300 pb^-1, the discovery and exclusion sensitivities rise to 490 GeV and 600 GeV. These scenarios are therefore among the most promising for dark matter at colliders. Perhaps most interestingly, we find that dark matter models that can explain results from the DAMA, CDMS and CoGeNT Collaborations can be tested with high statistical significance using data already collected at the Tevatron and have extraordinarily promising implications for early runs of the LHC.Comment: 22 pages; v2: additional discussion of relation to DAMA, CDMS, and CoGeNT results, references adde

Mobile Communication with Virtual Network Address Translation

Virtual Network Address Translation (VNAT) is a novel architecture that allows transparent migration of end-to-end live network connections associated with various computation units. Such computation units can be either a single process, or a group of processes of an application, or an entire host. VNAT virtualizes network connections perceived by transport protocols so that identification of network connections is decoupled from stationary hosts. Such virtual connections are then remapped into physical connections to be carried on the physical network using network address translation. VNAT requires no modification to existing applications, operating systems, or protocol stacks. Furthermore, it is fully compatible with the existing communication infrastructure; virtual and normal connections can coexist without interfering each other. VNAT functions entirely within end systems and requires no third party proxies. We have implemented a VNAT prototype with the Linux 2.4 kernel and demonstrated its functionality on a wide range of popular real-world network applications. Our performance results show that VNAT has essentially no overhead except when connections are migrated, in which case the overhead of our Linux prototype is less than 7 percent

B's with Direct Decays: Tevatron and LHC Discovery Prospects in the b\bar{b}+MET Channel

We explore the discovery prospects for B'\bar{B}' pair production followed by direct decays B'->bX, where B' is a new quark and X is a long-lived neutral particle. We develop optimized cuts in the (m_B', m_X) plane and show that the 7 TeV LHC with an integrated luminosity of 1 (10) fb^-1 may exclude masses up to m_B' ~ 620 (800) GeV, completely covering the mass range allowed for new quarks that get mass from electroweak symmetry breaking. This analysis is applicable to other models with b\bar{b}+MET signals, including supersymmetric models with bottom squarks decaying directly to neutralinos, and models with exotic quarks decaying directly to GeV-scale dark matter. To accommodate these and other interpretations, we also present model-independent results for the b\bar{b}+MET cross section required for exclusion and discovery.Comment: 18 pages; v2: published versio

Endocide-Induced Abnormal Growth Forms of Invasive Giant Salvinia (Salvinia molesta)

Giant salvinia (Salvinia molesta) is one of the most noxious invasive species in the world. The fern is known to have primary, secondary, and tertiary growth forms, which are also commonly hypothesized as growth stages. The identification of these forms is primarily based on the size and folding status of the floating leaves. However, we identified 12 forms in the greenhouse and the field. Our experiments showed that the folding of floating leaves is a reversible trait dependent on water access. The floating leaves quickly fold in response to water shortage, reducing water loss and needs, decreasing growth, and avoiding trichome damage. The leaves re-open to allow trichomes repel water and enhance growth when having adequate water supply. Larger secondary or tertiary forms do not produce small-leaf primary forms without high intensity stress. These results do not support the hypothesis that three growth forms represent sequential growth stages. The abnormal small-leaf forms are the result of endocide-induced autotoxicity and some of them never grow into other forms. The development of abnormal forms and reversible leaf folding strategy in response to high stress along with rapid asexual reproduction are major adaptive traits contributing to the invasiveness of S. molesta

Measurements of Isoprene-Derived Organosulfates in Ambient Aerosols by Aerosol Time-of-Flight Mass Spectrometry—Part 2: Temporal Variability and Formation Mechanisms

Organosulfate species have recently gained attention for their potentially significant contribution to secondary organic aerosol (SOA); however, their temporal behavior in the ambient atmosphere has not been probed in detail. In this work, organosulfates derived from isoprene were observed in single particle mass spectra in Atlanta, GA during the 2002 Aerosol Nucleation and Characterization Experiment (ANARChE) and the 2008 August Mini-Intensive Gas and Aerosol Study (AMIGAS). Real-time measurements revealed that the highest organosulfate concentrations occurred at night under a stable boundary layer, suggesting gas-to-particle partitioning and subsequent aqueous-phase processing of the organic precursors played key roles in their formation. Further analysis of the diurnal profile suggests possible contributions from multiple production mechanisms, including acid-catalysis and radical-initiation. This work highlights the potential for additional SOA formation pathways in biogenically influenced urban regions to enhance the organic aerosol burden

Association of the tensin N-terminal protein-tyrosine phosphatase domain with the alpha isoform of protein phosphatase-1 in focal adhesions

Focal adhesions attach cultured cells to the extracellular matrix, and we found endogenous protein phosphatase-1alpha isoform (PP1alpha) localized in adhesions across the entire area of adherent fibroblasts. However, in fibroblasts migrating into a scrape wound or spreading after replating PP1alpha did not appear in adhesions near the leading edge but was recruited into other adhesions coincident in time and space with incorporation of tensin. Endogenous tensin and PP1alpha co-precipitated from cell lysates with isoform-specific PP1 antibodies. Chemical cross-linking of focal adhesion preparations with Lomant\u27s reagent demonstrated molecular proximity of endogenous PP1alpha and tensin, whereas neither focal adhesion kinase nor vinculin was cross-linked and co-precipitated with PP1alpha, suggesting distinct spatial subdomains within adhesions. Transient expression of truncated tensin showed the N-terminal 360 residues, which comprise a protein-tyrosine phosphatase domain, alone were sufficient for isoform-selective co-precipitation of co-expressed PP1alpha. Human prostate cancer PC3 cells are deficient in tensin relative to fibroblasts and have fewer, mostly peripheral adhesions. Transient expression of green fluorescent protein tensin in these cancer cells induced formation of adhesions and recruited endogenous PP1alpha into those adhesions. Thus, the protein-tyrosine phosphatase domain of tensin exhibits isoform-specific association with PP1alpha in a restricted spatial region of adhesions that are formed during cell migration

MobiDesk: Mobile Virtual Desktop Computing

We present MobiDesk, a mobile virtual desktop computing hosting infrastructure that leverages continued improvements in network speed, cost, and ubiquity to address the complexity, cost, and mobility limitations of today's personal computing infrastructure. MobiDesk transparently virtualizes a user's computing session by abstracting underlying system resources in three key areas: display, operating system and network. MobiDesk provides a thin virtualization layer that decouples a user's computing session from any particular end user device and moves all application logic from end user devices to hosting providers. MobiDesk virtualization decouples a user's computing session from the underlying operating system and server instance, enabling high availability service by transparently migrating sessions from one server to another during server maintenance or upgrades. We have implemented a MobiDesk prototype in Linux that works with existing unmodified applications and operating system kernels. Our experimental results demonstrate that MobiDesk has very low virtualization overhead, can provide a full-featured desktop experience including full-motion video support, and is able to migrate users' sessions efficiently and reliably for high availability, while maintaining existing network connections

Mechanism of action of VP1-001 in cryAB(R120G)-associated and age-related cataracts

PurposeWe previously identified an oxysterol, VP1-001 (also known as compound 29), that partially restores the transparency of lenses with cataracts. To understand the mechanism of VP1-001, we tested the ability of its enantiomer, ent-VP1-001, to bind and stabilize αB-crystallin (cryAB) in vitro and to produce a similar therapeutic effect in cryAB(R120G) mutant and aged wild-type mice with cataracts. VP1-001 and ent-VP1-001 have identical physicochemical properties. These experiments are designed to critically evaluate whether stereoselective binding to cryAB is required for activity.MethodsWe compared the binding of VP1-001 and ent-VP1-001 to cryAB using in silico docking, differential scanning fluorimetry (DSF), and microscale thermophoresis (MST). Compounds were delivered by six topical administrations to mouse eyes over 2 weeks, and the effects on cataracts and lens refractive measures in vivo were examined. Additionally, lens epithelial and fiber cell morphologies were assessed via transmission electron microscopy.ResultsDocking studies suggested greater binding of VP1-001 into a deep groove in the cryAB dimer compared with ent-VP1-001. Consistent with this prediction, DSF and MST experiments showed that VP1-001 bound cryAB, whereas ent-VP1-001 did not. Accordingly, topical treatment of lenses with ent-VP1-001 had no effect, whereas VP1-001 produced a statistically significant improvement in lens clarity and favorable changes in lens morphology.ConclusionsThe ability of VP1-001 to bind native cryAB dimers is important for its ability to reverse lens opacity in mouse models of cataracts